System and method of authentication of an electronic signature

ABSTRACT

A system and method supporting signature verification. An input signature from a contact point of a stylus at a touch-sensitive surface is received. At least one sensor detects a first set of characteristics of the input signature that represents how the stylus is used when a present security level is a first level, and a second set of characteristics is determined when a present security level is a second security level. The second set of characteristics is a subset of the first set with fewer characteristics than the first set. One of the first set of characteristics or the second set of characteristics is transmitted to a characteristic receiving device to permit the input signature to be authenticated as a function, at least in part, of the first set or the second set of characteristics.

FIELD OF TECHNOLOGY

The present disclosure relates generally to a system and method ofauthentication and specifically to a system and method of multi-factorauthentication of an electronic signature using a stylus input.

BACKGROUND

Handwritten signatures are commonly used in payment operations today toverify that a purchaser or sender of money is authorized to make atransaction. It is important to verify the identity of the personperforming the operation. Handwritten signatures are generally used todo this. However, handwritten signatures can easily be forged and it isdifficult to truly authenticate other technologies, including theentering of a personal identification number (PIN). Recently, electronicsignatures have become more common, including entering a signature on adigital surface.

Authentication of a person requesting access typically comprisescomparing a signature image with a pre-stored image. Signatures can becopied with relative ease thus requiring multi factor authenticationsuch as passwords, PIN entry and/or biometric scanners, includingfingerprint or retina scans to positively identify the user.Multi-factor authentication can be cumbersome and confusing, requiringequipment and remembering of passwords.

Various styli are known. Typically, a stylus serves in conjunction witha scribing surface that is configured to work with the correspondingstylus. Generally speaking, a stylus is typically a hand-held writingtool that often (but not exclusively) has a pencil-like elongated formfactor and that includes at least one pointed end configured to interactwith a scribing surface. Using a stylus as an input mechanism offers avariety of advantages over a fingertip including the opportunity forincreased precision as well as an expression modality that accords withthe user's own past experience with a pencil or pen.

Together with a display, a stylus can at least serve to cause thedisplay of a so-called electronic-ink line that tracks and correspondsto movement of the stylus on the scribing surface. Such an inputmodality permits the user to enter text or to draw an image.

In some cases, a device might be locked and require a password. This canbe done via text entry, PIN entry, or biometric authentication.

Existing stylus-based modalities do not necessarily meet the needs ofall users for accessing the device since an additional mode ofauthenticating a user is often needed.

BRIEF DESCRIPTION OF DRAWINGS

Reference will now be made, by way of example, to the accompanyingdrawings which show example implementations; and in which:

FIG. 1 is a flow diagram illustrating a method of the stylus, inaccordance with an embodiment of the present disclosure.

FIG. 2 is a block diagram of an example of a stylus barrel, inaccordance with an embodiment of the present disclosure.

FIG. 3 is a flow diagram illustrating a method of the host, inaccordance with an embodiment of the present disclosure.

FIG. 4 is a block diagram of an example of a host, in accordance with anembodiment of the present disclosure.

FIG. 5A is a graphical illustration of the x-component of tiltinformation vs time, in accordance with an embodiment of the presentdisclosure.

FIG. 5B is a graphical illustration of the first derivative of thex-component of tilt information vs time, in accordance with anembodiment of the present disclosure.

FIG. 5C is a graphical illustration of the x-component of positioninformation vs time, in accordance with an embodiment of the presentdisclosure.

FIG. 5D is a graphical illustration of the x-component of velocityinformation vs time, in accordance with an embodiment of the presentdisclosure.

FIG. 5E is a graphical illustration of the x-component of accelerationvs time, in accordance with an embodiment of the present disclosure.

FIG. 5F is a graphical illustration of pressure information vs time, inaccordance with an embodiment of the present disclosure.

FIG. 6 is a block diagram of a system, in accordance with an embodimentof the present disclosure.

FIG. 7 is a flow chart of a method of the system based on a securitylevel.

DETAILED DESCRIPTION

The following describes an apparatus and method pertaining to detectinga user's input with respect to a stylus and wireless transmission ofinformation regarding characteristics of the input. The input capturesvarious characteristics extracted from profiles of the signature. Thedetected characteristics of the input can comprise, for example, thespeed of the input or the angle of entry. This specification is directedto a system and method for authenticating a signature input through awriting instrument based on different properties of the profile of thesignature. The signature is detected by accelerometer sensors present inthe stylus, which is used as a writing instrument. Variouscharacteristics of the input received through the stylus are detected bythe stylus circuitry. The input is transmitted to a host authenticationdevice which determines whether the user of the instrument isauthenticated. An input receiving device is a device on which the stylusis in contact with or in proximity to while in use for signing. Theinput receiving device may have a touch-sensitive surface on the front,back, sides or corners of the device.

The host can be a secondary device or a server. Preferably the host is amobile device such as a tablet writing surface upon which the stylusprovides the input. The host may also be a smartphone. The host has atouch panel which receives the input from the stylus and contains astylus sensor, such as a digitizer which converts the input into digitalcode. If the host is a secondary device, the writing surface will thenwirelessly transmit the signature information to the secondary device.The secondary device may also be referred to as a characteristicreceiving device. The stylus is an extension of the host and is inwireless communication with the host. There may also be a server inwireless communication with the host and remote storage. The remotestorage may include a cloud service, a database, the internet, oranother repository for storing information obtained from the host thatmay be retrieved upon request.

The input receiving device may, in some cases, be the same as thecharacteristic receiving device. For example, if the stylus is used towrite or sign on a host, and the host itself saves the templateinformation and performs the authentication, without reliance on anadditional server, then the host is the input receiving device as wellas the characteristic receiving device.

The digitizer is an electronic component within the host that wirelesslycommunicates with the stylus. The digitizer receives transmittedinformation from the stylus and based on the received information, thedigitizer is able to determine the position of the stylus with respectto the host surface. The digitizer performs the tracking mechanism ofthe stylus since it is able to report the position of the stylus withrespect to the surface of the host or screen surface. The digitizer mayalso report the position while the stylus is in hover mode, that is thestylus is in proximity to, for example within a few millimeters, but nottouching the screen surface. The digitizer itself is housed within thehost and electronically connected to the processor of the host.

The stylus itself may be active or passive. An active stylus emits asignal, via an antenna or transducer, and enables the system to listenpassively. A passive stylus receives input through button events via auser sensor 204 retrieved through the digitizer or through the wirelesslink, through force applied to the stylus tip which is retrieved throughthe digitizer or through the wireless link, or through acceleration androtation of the stylus body which is retrieved through the wireless linksuch as Bluetooth™ An active stylus can transfer data to the host inmultiple ways in parallel such as by sending a full set of parametersover the Bluetooth™ link. It may also send only a specific element, suchas a password, through the digitizer. The host will then compare thedata received and perform a security check of the data received. Sincethe digitizer can retrieve the signal from the active stylus in closeproximity, the host may determine that data was sent through theBluetooth™ link by the active stylus that is in contact with the screensurface.

These teachings are also highly flexible in practice. As one example inthese regards, the foregoing gesture information can be wirelesslytransmitted along with other information. This other information caninclude, for example, information regarding one or more stylus operatingcircumstances (such as, but not limited to, a present angle ofinclination of the stylus, rotation of the stylus about its longitudinalaxis, and so forth).

These teachings are readily employed with any of a wide variety ofstylus types including, but not limited to, capacitively-based styli,acoustically-based non-passive styli, magnetically-based non-passivestyli, light-emitting-based non-passive styli, camera-based non-passivestyli, radio-frequency-based non-passive styli, and so forth.

For simplicity and clarity of illustration, reference numerals may berepeated among the figures to indicate corresponding or analogouselements. Numerous details are set forth to provide an understanding ofthe embodiments described herein. The embodiments may be practicedwithout these details. In other instances, well-known methods,procedures, and components have not been described in detail to avoidobscuring the embodiments described. The description is not to beconsidered as limited to the scope of the embodiments described herein.

FIG. 1 presents a process 100 that accords at least in part with many ofthese teachings. For the sake of an illustrative example it will bepresumed here that a control circuit for a stylus carries out thisprocess 100. Again for the purpose of illustration and without intendingany limitations in these regards, FIG. 2 presents an example of such astylus 200. In particular, in this example, the stylus 200 includes astylus barrel 201 that contains (at least in part) the aforementionedcontrol circuit 202. In a typical application setting this stylus barrel201 has a pen or pencil-like form factor and is shaped and configured tobe comfortably grasped and manipulated by a user's hand. Styli barrelsare well known in the art. As the present teachings are not overlysensitive to any particular selections in these regards, furtherelaboration regarding styli barrels is not provided here for the sake ofbrevity.

The control circuit 202 can comprise a fixed-purpose hard-wired platformor can comprise a partially or wholly programmable platform. Thesearchitectural options are well known and understood in the art andrequire no further description here. This control circuit 202 isconfigured (for example, by using corresponding programming as will bewell understood by those skilled in the art) to carry out one or more ofthe steps, actions, and/or functions described herein.

By one optional approach the control circuit 202 operably couples to amemory 203. This memory 203 may be integral to the control circuit 202or can be physically discrete (in whole or in part) from the controlcircuit 202 as desired. This memory 203 can serve, for example, tonon-transitorily store the computer instructions that, when executed bythe control circuit 202, cause the control circuit 202 to behave asdescribed herein. (As used herein, this reference to “non-transitorily”will be understood to refer to a non-ephemeral state for the storedcontents (and hence excludes when the stored contents merely constitutesignals or waves) rather than volatility of the storage media itself andhence includes both non-volatile memory, such as read-only memory (ROM)as well as volatile memory, such as Random Access Memory (RAM).

In this illustrative example the control circuit 202 also operablycouples to one or more user sensors 204 and a wireless transmitter 206.The user sensor 204 is also supported by the stylus barrel 201 and isconfigured to detect at least one characteristic of the input of auser's gesture with respect to the stylus barrel 201 from a contactpoint of the stylus with a surface. By one approach, for example, theuser sensor 204 can comprise one or more electrically-conductive sensors(including but not limited to capacitively-based sensors as are known inthe art) and/or one or more optical-based sensors (including but notlimited to an image-capture component such as a camera oriented tocapture images of part or all of the user's hand and/or one or morefingers or thumb). (As used herein the expression “user sensor” will beunderstood to not comprise a mere button, slide switch, or the like.)

The aforementioned wireless transmitter 206 can also be supported by thestylus barrel. This wireless transmitter 206 can employ aradio-frequency carrier or an optical carrier (such as an infra-redcarrier) as desired. Generally speaking, for most application settingsthis wireless transmitter 206 need only support a short-range technology(such as, but not limited to, the Bluetooth™ standard or the unlicensedcordless-microphone spectrum). A short-range approach will suffice formany application settings as the distance between the stylus 200 and itscorresponding scribing surface/stylus sensor is usually on the order ofless than only a very few inches. Other examples of possible short-rangetechnologies include Near Field Communications (NFC), Infrared (rDA),Wi-Fi and other technology at wavelengths in between or a combination oftechnologies that would be known to a person skilled in the art.

NFC can be used to send characteristic information data determined bythe stylus to the host. NFC can also be used to securely transmit apassword in order to validate data. An active stylus can also transmitemitted signals over NFC.

In an alternate embodiment, NFC could be used by transmittingcharacteristic information by using a stylus on a surface that isdifferent from the host. In this way, the stylus can capturecharacteristic information such as position, velocity, acceleration andtilt. Ultrasonic technology may also transmit information related to thevibration of materials when pressure is applied on it. The use oftriangulation may assist the system in determining the location of thestylus with respect to the host device. Ultrasonic technology can sendencrypted information in the frequency range of approximately 20-100kHz.

In an alternate embodiment, a plurality of additional sensors may beplaced on the back cover of a host device, on the corners of the hostdevice, or on the sides of the host device. The orientation of thedevice may be determined by the sensors embedded therein, and any of thesigning surfaces may transmit information related to which surface isbeing signed. For example, a user may record their template signature onthe top right corner of the device. If an unauthorized entity attemptsto replicate a signature with similar characteristic information but onthe back cover instead of the top right corner, the entity would not beauthenticated. In this way, the orientation of the device can provide anadditional level of security.

In an additional embodiment, a signature input on the device can bedisplayed on the display of the device or another screen or monitorassociated with the device.

If desired, the stylus 200 may also optionally include a stylusoperating circumstance sensor 205 that also operably couples to thecontrol circuit 202. An example of a stylus operating circumstancesensor 205 includes, for example, an accelerometer, a tilt detector, andso forth. So configured, the control circuit 202 can be configured todetect one or more stylus operating circumstances (such as, but notlimited to, an angle of inclination of the stylus 200, rotation of thestylus 200 about its longitudinal axis, and so forth).

With continued reference to FIGS. 1 and 2, such a control circuit 202can, at 101, detect a user's gesture with respect to the stylus 200. Thepresent teachings are highly flexible in these regards and willaccommodate a wide variety of user gestures. The gesture of the userindicates the stylus is being used to write with and data detection thenbegins. This distinguishes any general movement of the stylus from beingconsidered a characteristic.

Returning to FIGS. 1 and 2, this process 100 will accommodate at 102,detecting at least one stylus characteristic (using, for example, theaforementioned stylus operating circumstance sensor 205). As one simple,non-limiting example in these regards, the detected stylus operatingcircumstance could comprise, at least in part, an angle of inclinationof the stylus 200 (with respect to, for example, the scribing surfaceupon which the stylus 200 moves). Where a given gesture might indicatethat a line thickness is to change, the tilt of the stylus 200 couldserve, for example, to indicate an amount by which the line thickness isto increase or decrease (either in absolute terms or in relative termsas desired).

At 103 the control circuit 202 transmits information regarding thestylus input. The information is transmitted to a host authenticationdevice. The host authentication device may be connected by a wireconnection to the stylus, or it may be in wireless communication withthe stylus. The wireless communication may be over Bluetooth™.

The input information is transmitted, by the stylus, in a highlysecurable file that may include cyclic redundancy checks (CRC) to ensurethe integrity of the data. Authentication may be done on the host levelto verify the information has been received and is complete. Thesecurity of the file is important to prevent the file from beingaccessed by third parties. In the case of transmitting the filewirelessly to the host device, it is also necessary to provideidentification information such that the stylus file is not incorrectlytransmitted to a host device that is different from the intended one.

Referring to FIG. 3, the host receives the transmitted file containingthe characteristic from the stylus 310. The host then compares thereceived characteristics to a predefined stored template or value 320.If a match 330 is determined to exist, within reasonable tolerances inthe security field of art, a match is verified and the action desired bythe stylus 350 will be permitted to be performed. A graphical display toindicate success of the verification may be displayed to the user. Theaction could be a financial transaction that the user is using thestylus to sign for, it could be receiving a shipment, or any otherapplication of writing or signing that requires rapid authentication. Itcould also be an action to unlock the host device, and once the templateis verified, device becomes unlocked. Any application in which apassword is typically required can be replaced by this method ofauthentication. In case the characteristic of the signature does notmatch the template, a display message 340 may be displayed. This displaymessage could include an alert indicating the user is not the authorizeduser or it could display a warning requesting the user to try again.

An additional embodiment comprising a higher level of security includesstoring the predefined template on the remote server. The remote serverwould perform the validation of the signature upon request. This resultsin an additional level of security because the predefined signaturewould be protected against theft, alternation or reproduction. Thisembodiment also permits a user to sign from multiple terminals such as,but not limited to, a tablet, a smartphone, a personal computer, orothers. The stored template would not be on the local device thereforethe authentication would not be limited to a single device.

Referring to FIG. 4, a given electronic device 400 can be configured toreceive and utilize the aforementioned transmission. Such a device 400can include its own control circuit 401 that operably couples to amemory 402, a stylus sensor 403, a display 404, and a wireless receiver405. The stylus sensor 403 can serve, for example, to detect and trackthe stylus's contact with and movement across a given scribing surface.An example of a stylus sensor is a digitizer. The control circuit 401can then provide a corresponding presentation of electronic ink on thedisplay 404 that correlates to that tracked contact/movement. Suchpractices are known in the art. Accordingly, further elaboration inthese regards here will not be provided for the sake of brevity.

The wireless receiver 405 is configured in this example to compatiblyreceive the transmissions of the aforementioned wireless transmitter206. When the wireless transmitter 206 comprises a Bluetooth™-compatibletransmitter, for example, the wireless receiver 405 can itself comprisea Bluetooth™-compatible receiver.

The control circuit 401 of this device 400 can be configured tointerpret the received signals from the stylus 200 as regards theaforementioned detected gestures to thereby facilitate an additionaluser-input modality by which the user can control, influence, andeffect, for example, the ways by which the device 400 interprets andutilizes stylus-based scribing input.

The user sensor 204 can include an accelerometer in the stylus and maybe used to capture tilt angle, acceleration, duration and palm restingtime. The accelerometer may be a real-time sensor which can capturevarious stylus related parameters such as, but not limited to, pressureimparted from the stylus to a touch-sensitive surface. The pressure maybe imparted while the user of the stylus signs in a manner analogous toa handwritten signature. Pressure may also include force. Potentialpressure sensors that may be used to detect pressure and force includepiezo sensors, resistive inks, resistive carbon, strain gauge, barometersensors, gauge pressure sensors, optical-mechanical sensors and othersensors that would be known to a person skilled in the art.

As a security feature, the stylus related parameters or characteristicsmay then be stored and transmitted to a host. The host may be a handheldmobile device, a server, or any additional location where a predefinedtemplate is stored. Other types of user sensors 204 that could be usedin the stylus to capture characteristic information include3-dimensional sensors such as gyroscopes which can capture rotation, andmagnetometers. The use of a magnetometer may assist a gyrometer andaccelerometer in making improved measurements. A magnetometer canprovide more accuracy, and calibration or re-calibration of theaccelerometer and gyrometer. This is because the magnetic field of theearth will always be known and so the determination of the tilt angle,for example, with respect to a surface can be more accurately determinedwith the assistance of the magnetic field.

One characteristic includes, but is not limited to, the trajectory ofthe stylus tip tracking the signature. Typical position sensors are ableto capture displacement, however the use of additional 3-dimensionalsensors may work in co-ordination with the position sensors to increasethe accuracy of position sensors.

Acceleration and deceleration of the stylus as the user proceeds to signmay also be captured by accelerometers. These characteristics may be afunction of the size of a user's hand, whether the user is right or lefthanded, as well as the uniqueness of their handwritten signature. All ofthis information may be captured by the accelerometer and subsequentlycompared to a stored template.

Accelerometer measurements are made with respect to an arbitrary frameof reference of the stylus so a gyroscope may be used to assist inmapping accelerometer measurements onto a fixed frame of reference priorto single integration for velocity and double integration for positionmeasurements. By using a 3-dimensional gyroscope, a 3-dimensionalrotation matrix may be maintained which is multiplied against theaccelerometer measurements in order to resolve them on a fix frame ofreference. This may be chosen as the orientation of the stylus at theinitial point of the signature input motion. Since the duration of thesignature is generally within a few seconds, this brief duration allowsfor limited time for integration errors to build.

Single integration provides velocity information, which is the mostvaluable data from the dead reckoning sensors, and also provides lessintegration error than the errors inherent with double integration.

The results of double integration to get position may be blended withthe trajectory of the tip of the stylus that has been captured by othermeans. Typically, a user may lift the stylus between letters, to dot orcross a letter, or underline. Therefore additional information may alsobe captured on the z-axis.

Another characteristic to be captured may be the stylus tip pressure.Typically, the residue of the pressure related information is whatgraphologists look for when analyzing handwritten signatures on paper.The pressure history of a signature, may therefore be an additionalunique characteristic that can be captured by an individual's signaturewritten in real-time.

One advantage of this method of authentication is the significantlyreduced likelihood of a forged signature. Since multiple parameters maybe obtained and saved to accurately capture a users signature, it wouldrequire many hours of practice to replicate all of the variables. Thelikelihood of replicating all of the parameters in real-time is reduced.Therefore, extraction of multiple characteristics from sensors resultsin increased insight that graphologists would be unable to obtainthrough handwriting analysis.

In addition to individual characteristics being stored and transmitted,profiles may be created which incorporates multiple characteristics intoa single profile. Examples of profiles may be dynamic force profiles,pressure profiles, tilt angle profiles, acceleration profiles, positionprofiles, rotation profiles or velocity profiles. A characteristic maybe defined as a measurement taken at a single point in time or space,whereas as a profile refers to characteristics recorded across anextended time period or distance. Distance can be along the complextrajectory of the stylus tip, or between the start and end of the wholesignature trajectory.

A component of the position profile may also indicate the time durationof active input entry. This may be shown by the control circuitryremoving the time segments during which the user pauses. An additionalcomponent of the position profile may indicate the time duration ofinput inactivity during input entry. This may be shown by the controlcircuitry removing the time segments during which the user is writingand only indicating the time duration during which the user pauses.

Various characteristics of a signature may be captured individually orcollectively. A plurality of characteristics form a profile. Thesecharacteristics may be compiled together to form a profile and thenrecorded by the internal circuitry of the stylus 205 collectively andtransmitted to the host together for comparison to a stored profile.

The dynamic force profile may be saved when the user imposes a force onthe stylus tip while writing the signature. In this case, the styluscircuit will record how much force is input on the signature atdifferent positions while signing. This could be emitted based onletters or curves of the signature, and segments of distance on thesurface or force per unit time.

A profile may also be defined in terms of tilt angle of the stylus.While the stylus is being held in the users hand, there is an angle ofincidence between the tip of the stylus and the writing surface. Thisangle can be saved as a characteristic at a point in time, or the tiltangle profile can be defined by a set of tilt angle characteristicsrecorded over a distance or a time interval.

Acceleration or velocity profiles of the stylus may be saved. Theacceleration and velocity measurements may be recorded by the stylus atindividual positions as the stylus is moving across the surface, perdistance or per unit in time, thus defining an acceleration profile or avelocity profile.

The profile may also be defined in terms of time. Either the timeduration of the signature while the stylus is active can be recorded, orthe time duration of the signature while the palm is in a resting statecan be saved. Individuals will typically take varying amounts of timewhile writing and while pausing when completing a signature. All ofthese time measurements may be captured for comparison to thepre-defined template.

After recording the characteristics or profiles, the stylus relays thedata by transmitting it to a host device for authentication. The hostdevice may comprise a tablet, a server, or a database. When the recordeddata is transmitted to the host, it proceeds to retrieve a storedtemplate of information. The information contained in the template iscompared to the characteristic or profile information that was obtainedfrom the stylus. If the template information matches the stylusinformation, the user has been successfully authenticated and theoperation may be permitted.

The transmitted characteristic received by the host may include atransmitted velocity of the input, a transmitted pressure of the input,a profile defining a dynamic force profile, a tilt angle profile, anacceleration profile, and a position profile. The position profile mayinclude an indication of the time duration of active input entry and atime duration of input inactivity during which the user is not activelysigning.

Optionally, additional characteristics could be stored as part of thesignature template as well as the received signature. Examples ofadditional characteristics include date and location. The location canbe obtained via a GPS on the host device, triangulation based on signalstrength of surrounding radio towers, user input through an interface onthe host, or any other means that enables the device to record thecurrent location of the device.

The combination of the characteristics of location and date, withappropriate corresponding hardware sensors that a person skilled in theart would know how to add in order to test these conditions. wouldenable additional parameters to be derived from these characteristics.For example, if the signature was signed outside, environmentalconditions at the location and at the time of the signature could beincorporated. These conditions may include altitude, atmosphericpressure, humidity coefficient, sunny conditions, cloudy conditions, andprecipitation. The presence or absence of specific features within aspecific range allows for tolerances in distinguishing characteristicsof the profile.

Typically, during the time it takes for a user to sign their signsignature, atmospheric pressure does not fluctuate. Therefore, for thepurpose of handwriting analysis, it would be possible to use an absolutepressure sensor such as a barometer to determine the pressure applied bythe stylus during signing.

Since factors including location and environmental conditions would beconsiderably more difficult to impersonate, incorporating such factorsprovides an additional and robust method of validating an authenticsignature.

The stylus may be connected by a wire to the host. In this case, thedata transfer is direct and immediate. The host contains the storedtemplate information and performs the authentication is real time. Thestylus may also transmit the characteristic information wirelessly to ahost that is not directly connected. A wireless transfer is done over anactive link and a decoder is used to decode a signal from a shortrangetechnology, such as Bluetooth™ signal. In addition, there is adifference between rotation and tilt in capturing information related toa signature. Character analysis is also an important distinguishingfactor as the direction which a user writes can be taken into account. Asignature may be passive, that is the letters are slanting backwards,aggressive with forward slanting letters, cautious with the signaturerestricted to an imaginary line, intelligent with few lifts of thestylus and consistent letter flow. Similar categories known in the fieldof character analysis may be defined and such intelligent analysis canbe added to the algorithm for tracking the security of signature.

FIG. 5A-5F illustrate graphically examples of various characteristicsfor a signature, plotted in a characteristic versus time for thesignature. FIGS. 5A to 5F shows the characteristics in the x-direction,however similar data for the y- and z-directions could also be plotted.Additional characteristics obtained and incorporated into a signatureprofile enhance the security level. For example, if only the position inthe x-direction is compared, there is a minimum level of securitypresent that could be copied. However if additional information in they- and z-directions are also recorded, the chances of copying thisinformation is significantly reduced.

Different security levels may be defined depending on the minimum numberof security levels required. If a higher level security is required, apredefined threshold such as 10 characteristics may be required. If alower level of security is required, perhaps only verification of 2characteristics are sufficient. The minimum security level may bedefined by an administrator policy or could be selected by a user.

The digital measurements recorded can be reconstructed into an examplesignature as well. Each of the measurements can also be stored within anacceptable tolerance level. The tolerance can also be different for eachcharacteristic.

FIG. 5A-5F illustrate examples of what digital measurements are storedin a database to compare against an input signature. The computer plotselectronically characteristics that define a human signature profile. Aprofile may be a single characteristic or a combination of a pluralityof characteristics.

FIG. 5A illustrates the x-component of the tilt angle as it changesthrough the time it takes a person to sign. If an unauthorized personattempted to replicate a signature with a different tilt in thex-direction, the algorithm would not match the attempt with the templateand access would be denied.

FIG. 5B illustrates the x-component of the first derivative of the tiltangle as it changes through time. This is a calculated value determinedfrom the measured value shown in FIG. 5A.

FIG. 5C illustrates the x-component of the position of the stylus as theuser signs the signature on the paper. Similar values in the y-directionmay indicate the height of a letter and in the z-direction may indicateif a user crossed or dotted a letter.

FIG. 5D illustrates the x-component of the velocity of the stylus as itchanges through time. This shows the speed at which the user signs theirname.

FIG. 5E illustrates the x-component of the acceleration of the stylus asit changes through time. This shows the rate at which the user speeds upor slows down the signing of their name.

FIG. 5F illustrates the pressure of the stylus as a user presses on thesurface while signing. The host can include a smartphone, tablet,superphone, a device that has the ability to navigate using a trackpad,or any other type of electronic device.

FIG. 6 is an example of the system which includes the host 400incorporating the stylus sensor, specifically a digitizer 404 fortracking the characteristics of the stylus 610. The stylus 610 is inwireless communication with the host 400. The host may also transmit andreceive information with a server 620. The server 620 may storeinformation such as a template to compare the received signature with.If the template stored on the server 620 matches the informationtransmitted from the stylus 610 and received by the host 400, then thesignature will be authenticated. It is also possible for additionalinformation including signature templates to be stored in a remotestorage location 630, such as a cloud. In this case, the server 620 willaccess the remote storage 630 to authenticate a received signature fromthe information transmitted by the stylus 610 through the host 400.

FIG. 7 illustrates an algorithm performed by the system to verify thecharacteristics based on a desired security level. Firs the stylustransmits the input received by the signing, 710. The desired securitylevel is determined, it may be predefined in categories or based on thedesired number of matching characteristics. In this example, adetermination is made 730 if the security level is “high”. If it is high720, the host records a predefined number of characteristics thatcorrespond to the desired level. If the level is not high 740, the hostrecords a different number of characteristics, where the number recordedat 740 is less than that would be recorded at 720.

The host then retrieves the template characteristics 750 that may bestored in remote storage 630. The host compares the input profile valueswith the template profile 760 and determines if the input is within anacceptable tolerance of the template 770. If the input is within thetolerance, the action is permitted 780. If the input is not within theacceptable tolerance of the template 780, the action is denied.

As understood by a person skilled in the art, a plurality ofcharacteristics may form a profile. The template profile may be comparedto the input profile insofar as the same types of characteristics arebeing compared. For example, if the security level indicates pressure isnot to be compared, the template profile related to pressure would notbe accessed.

The present disclosure may be embodied in other specific forms withoutdeparting from its essential characteristics. The described embodimentsare to be considered in all respects only as illustrative and notrestrictive. The scope of the disclosure is, therefore, indicated by theappended claims rather than by the foregoing description. All changesthat come within the meaning and range of equivalency of the claims areto be embraced within their scope.

1. A method, comprising: receiving an input signature from a contactpoint of a stylus at a touch-sensitive surface of an input receivingdevice as the stylus is used to sign a user's name; detecting, based ona present security level being a first security level, a first set ofcharacteristics of the input signature by at least one sensor thatrepresents how the stylus is used to sign the user's name; detecting,based on the present security level being a second security level, asecond set of characteristics of the input signature by at least onesensor that represents how the stylus is used to sign the user's name,the second set of characteristics being a subset of the first setcomprising fewer characteristics than the first set; and transmittingone of the first set of characteristics or the second set ofcharacteristics to a characteristic receiving device to permit the inputsignature to be authenticated as a function, at least in part, of thefirst set or the second set of characteristics.
 2. The method of claim1, wherein the at least one sensor comprises a magnetometer, and whereinat least one of the first set of characteristics or the second set ofcharacteristics comprises measurements made by the magnetometer and atleast one of a location measurement of the stylus or an accelerationmeasurement of the stylus.
 3. The method of claim 1, wherein at leastone of the first set of characteristics or the second set ofcharacteristics comprises an amount of rotation of the stylus around alongitudinal axis of the stylus while the stylus is used to sign theuser's name.
 4. The method of claim 1, wherein at least one of the firstset of characteristics or the second set of characteristics comprises ageographic location of the stylus where the stylus is used to sign theuser's name.
 5. A method comprising: determining a present securitylevel for a present authentication is one of plurality of levelscomprising at least a first level and a second level; receiving, by ahost device, a plurality of transmitted characteristics generated by acontrol circuit of a stylus, the plurality of transmittedcharacteristics representing how the stylus is used to sign a user'sname; authenticating a signature as entered by the user, theauthenticating being based on: determining, based on the presentsecurity level being the first level, that a first set ofcharacteristics in the plurality of transmitted characteristicscorresponds to a stored first set of values for the first set ofcharacteristics; and determining, based on the present security levelbeing the second level, that a second set of characteristics within theplurality of transmitted characteristics corresponds to a stored secondset of values for the second set of characteristics, the second set ofcharacteristics being a subset of the first set comprising fewercharacteristics than the first set; and performing an action based onthe authentication.
 6. The method of claim 5, wherein the plurality oftransmitted characteristics comprises at least one of a transmittedvelocity as corresponds to when the stylus is used to sign the user'sname or a transmitted pressure as corresponds to when the stylus is usedto sign the user's name.
 7. The method of claim 5, wherein thetransmitted characteristics comprise a magnetometer reading, and whereinat least one of the stored first set of values or the stored second setof values comprises values of measurements made by the magnetometer andat least one of a value of a location measurement of the stylus or avalue of an acceleration measurement of the stylus.
 8. The method ofclaim 5, wherein the transmitted characteristics comprise an amount ofrotation of the stylus around a longitudinal axis of the stylus whilethe stylus is used to sign the user's name, and wherein at least one ofthe stored first set of values or the stored second set of valuescomprises an amount of rotation of the stylus around a longitudinal axisof the stylus.
 9. The method of claim 5, wherein the transmittedcharacteristics comprise a location of the signature on atouch-sensitive surface, and wherein at least one of the stored firstset of values or the stored second set of values comprises a value of alocation of the signature on the touch-sensitive surface.
 10. The methodof claim 5, wherein the transmitted characteristics comprise ageographic location of an input receiving device where the stylus isused to sign the user's name, and wherein at least one of the first setof values or the second set of values comprises a value of a geographiclocation.
 11. A stylus comprising a stylus barrel; at least one sensorsupported by the stylus barrel configured to detect at least onecharacteristic of an input signature associated with use of the stylusfrom a contact point of the stylus with a surface, wherein the at leastone sensor comprises one of an accelerometer or a gyroscope; atransmitter supported by the stylus barrel; and a control circuitsupported by the stylus barrel and operably coupled to both the at leastone sensor and the transmitter, the control circuit configured to:receive the input signature; detect, based on a present security levelbeing a first security level, a first set of characteristics of theinput signature by the at least one sensor that represents how thestylus is used to sign the user's name; detect, based on the presentsecurity level being a second security level, a second set ofcharacteristics of the input signature by the at least one sensor thatrepresents how the stylus is used to sign the user's name, the secondset of characteristics being a subset of the first set comprising fewercharacteristics than the first set; and transmit one of the first set ofcharacteristics or the second set of characteristics to a characteristicreceiving device to permit the input signature to be authenticated as afunction, at least in part, of the first set or the second set ofcharacteristics.
 12. The stylus of claim 11, wherein the at least onesensor comprises a magnetometer, and wherein at least one of the firstset of characteristics or the second set of characteristics comprisesmeasurements made by the magnetometer and at least one of a locationmeasurement of the stylus or an acceleration measurement of the stylus.13. The stylus of claim 11, wherein at least one of the first set ofcharacteristics or the second set of characteristics comprises ageographic location of the stylus where the stylus is used to sign theuser's name.
 14. An electronic device comprising a memory and aprocessor configured to: determine a present security level for apresent authentication is one of plurality of levels comprising at leasta first level and a second level; receive, by a host device, a pluralityof transmitted characteristics generated by a control circuit of astylus, the plurality of transmitted characteristics representing howthe stylus is sued to sign the user's name; authenticate a signaturereceived from the user, the authenticating being based on: determining,based on the present security level being the first level, that a firstset of characteristics in the plurality of transmitted characteristicscorresponds to a stored first set of values for the first set ofcharacteristics; and determining, based on the present security levelbeing the second level, that a second set of characteristics within theplurality of transmitted characteristics corresponds to a stored secondset of values for the second set of characteristics, the second set ofcharacteristics being a subset of the first set comprising fewercharacteristics than the first set; and performing an action based onthe authentication.
 15. The electronic device of claim 14, wherein theplurality of transmitted characteristics comprises at least one of atransmitted velocity as corresponds to when the stylus is used to signthe user's name or a transmitted pressure as corresponds to when thestylus is used to sign the user's name.
 16. The electronic device ofclaim 14, wherein the transmitted characteristics comprise a geographiclocation of an input receiving device where the stylus is used to signthe user's name, and wherein at least one of the stored first set ofvalues or the stored second set of values comprises a geographiclocation.
 17. A non-transitory computer readable medium havinginstructions executable by a processor, the instructions comprisinginstructions configured to: receive an input signature from a contactpoint of a stylus at a touch-sensitive surface of an input receivingdevice as the stylus is used to sign a user's name; detect, based on apresent security level being a first security level, a first set ofcharacteristics of the input signature by at least one sensor thatrepresents how the stylus is used to sign the user's name; detect, basedon the present security level being a second security level, a secondset of characteristics of the input signature by at least one sensorthat represents how the stylus is used to sign the user's name, thesecond set of characteristics being a subset of the first set comprisingfewer characteristics than the first set; and transmit one of the firstset of characteristics or the second set of characteristics to acharacteristic receiving device to permit the input signature to beauthenticated as a function, at least in part, of the first set or thesecond set of characteristics.
 18. The non-transitory computer readablemedium of claim 17, wherein the at least one sensor comprises amagnetometer, and wherein at least one of the first set ofcharacteristics or the second set of characteristics comprisesmeasurements made by the magnetometer and at least one of a locationmeasurement of the stylus or an acceleration measurement of the stylus.19. The non-transitory computer readable medium of claim 17, wherein atleast one of the first set of characteristics or the second set ofcharacteristics comprises an amount of rotation of the stylus around alongitudinal axis of the stylus while the stylus is used to sign theuser's name.
 20. The non-transitory computer readable medium of claim17, wherein at least one of the first set of characteristics or thesecond set of characteristics comprises a geographic location of thestylus where the stylus is used to sign the user's name.
 21. Anon-transitory computer readable medium having instructions executableby a processor, the instructions comprising instructions configured to:determine a present security level for a present authentication is oneof a plurality of levels comprising at least a first level and a secondlevel; receive, by a host device, a plurality of transmittedcharacteristics generated by a control circuit of a stylus, theplurality of transmitted characteristics representing how the stylus isused to sign the user's name; authenticate a signature as entered by theuser, the authenticating being based on: determining, based on thepresent security level being the first level, that a first set ofcharacteristics in the plurality of transmitted characteristicscorresponds to a stored first set of values for the first set ofcharacteristics; and determining, based on the present security levelbeing the second level, that a second set of characteristics within theplurality of transmitted characteristics corresponds to a stored secondset of values for the second set of characteristics, the second set ofcharacteristics being a subset of the first set comprising fewercharacteristics than the first set; and perform an action based on theauthentication.
 22. The non-transitory computer readable medium of claim21, wherein the plurality of transmitted characteristics comprises atleast one of a transmitted velocity as corresponds to when the stylus isused to sign the user's name or a transmitted pressure as corresponds towhen the stylus is used to sign the user's name.
 23. The non-transitorycomputer readable medium of claim 21, wherein the transmittedcharacteristics comprise a magnetometer reading, and wherein at leastone of the stored first set of values or the stored second set of valuescomprises measurements made by the magnetometer and at least one of avalue of a location measurement of the stylus or a value of anacceleration measurement of the stylus.
 24. The non-transitory computerreadable medium of claim 21, wherein the transmitted characteristicscomprise an amount of rotation of the stylus around a longitudinal axisof the stylus while the stylus is used to sign the user's name, andwherein at least one of the stored first set of values or the storedsecond set of values comprises a value of an amount of rotation of thestylus around a longitudinal axis of the stylus.
 25. The non-transitorycomputer readable medium of claim 21, wherein the transmittedcharacteristics comprise a geographic location of the input receivingdevice where the stylus is used to sign the user's name, and wherein atleast one of the stored first set of values or the stored second set ofvalues comprises a value of a geographic location.